Abstract:
Planets have recently been discovered in circumbinary orbits. The first stage
of terrestrial planet formation is grain growth and settling, but direct
observation of this stage in the inner disk is challenging. No planet has yet
been found in a T Tauri system and the time scale for giant planet formation
is uncertain. The edge-on binary T Tauri system KH 15D provides a unique, but
time-limited, opportunity to address these issues. KH 15D is a T Tauri binary
system composed of a K1 and K7 star in a close, eccentric orbit viewed nearly
edge-on. A thin circumbinary ring of solids has precipitated within the
accretion disk and acts as a sharp-edged screen that occults the binary
orbit. Precession has caused the screen to move slowly across the orbit,
first fully covering and now slowly revealing the members. The time scale of
the precession requires that the ring be truncated near 4AU, most likely by a
giant planet. We propose to use GNIRS to determine the spectral
characteristics of the red light component, possibly a giant planet, and to
search for spectral signatures of the ring.